The thirty-kilometer mark was where the tunnel ceased to be a race and became a graveyard for ambition.
The initial adrenaline that had carried the rookies through the first hour had evaporated, replaced by the rhythmic, agonizing thud of feet hitting cold stone.
Gabriel's pace remained a constant, mathematical certainty. He was no longer just running; he was observing the breakdown of the human form.
To his left, a man with badge number 301 collapsed. He didn't fall forward; his legs simply gave out, and he slid down the wall like a puppet with its strings cut.
No one looked back. In this vacuum of empathy, Gabriel felt perfectly at home.
His Six Eyes—even through the veil of his shapeshifting disguise—were feeding him a constant stream of data.
He could see the micro-tears in the muscles of the runners around him, the way their lactic acid levels were spiking, and the erratic flickering of their dormant Nen nodes.
"You're still not even sweating," Killua remarked, his voice cutting through the heavy atmosphere. He was still on his skateboard, but his eyes were fixed on Gabriel's neck.
"Most people, even the pros, have at least a sheen of sweat by now. You look like you're standing in an air-conditioned room."
"Sweat is a cooling mechanism for an inefficient engine," Gabriel replied. "If the energy conversion is perfect, there is no waste heat to dissipate."
Killua narrowed his eyes. "You talk like a machine."
"Logic is often mistaken for coldness," Gabriel said, his gaze drifting forward.
Far ahead, the light from Satotz's lantern flickered against the damp walls. The examiner hadn't looked back once.
He was a pacer, a relentless metronome designed to grind the weak into the dust. Gabriel noticed that the distance between the lead pack and the tail-end was now nearly two kilometers.
The "filter" was working.
[Ding! Discovery Sign-In Triggered: The Whispering Echoes.]
[Detection: You have maintained a perfect pace for 40 kilometers without a fluctuation in heart rate.]
[Reward: 'Breath of the Sun' (Source: Demon Slayer - Basic Forms) — A specialized breathing style that optimizes oxygen intake and blood flow, granting explosive power and heat-based visual effects to physical strikes.]
Gabriel felt his lungs expand, his ribcage shifting to accommodate a new, profound depth of respiration.
He didn't need the stamina—the Limit Break already provided that—but the Breath of the Sun offered a way to weaponize his movement.
He began to practice the breathing pattern mid-run. With every inhale, a faint, invisible heat began to radiate from his core.
Beside him, Gon suddenly sniffed the air. "Does anyone else smell... smoke? Or something hot?"
Killua looked around. "I don't smell anything. You're probably just smelling the friction of everyone's shoes."
Gabriel remained silent. He was now focusing on Leorio, who was approximately fifty meters behind them.
The man was a wreck. His tie was undone, his shirt was translucent with sweat, and his eyes were rolling in his head.
"He's hit the wall," Gabriel stated.
"Leorio? He's fine! He's just... really tired," Gon said, though he slowed his pace to look back.
"The human heart can only sustain that level of tachycardic stress for a finite period," Gabriel said, his voice devoid of emotion.
"Based on his current pallor and the rhythm of his stride, he will experience a total systemic shutdown within the next four hundred meters."
Kurapika, who had been running in a silent, vengeful trance, looked over at Gabriel. "You sound very certain of his failure."
"I am certain of the biology," Gabriel countered.
True to Gabriel's calculation, exactly three hundred and eighty meters later, Leorio stopped.
He didn't fall. He just stopped, his briefcase hitting the ground with a heavy thud. He stood there, head hanging, his aura so dim it was almost invisible.
Gon and Kurapika skidded to a halt.
"Leorio!" Gon shouted.
Gabriel didn't stop. He continued his
weightless glide, his back to the trio. To him, this was a crossroads.
If they stayed, they risked falling out of the "safe zone" of the lead pack. If they left him, they maintained their efficiency.
"Aren't you going to stop?" Killua asked, though he himself had slowed down to a hover on his board.
"I am not a doctor, nor am I his guardian," Gabriel said, his voice echoing back through the darkness. "The exam does not wait for those who lack the will to carry their own weight."
He kept moving. Behind him, he heard the sounds of a struggle—Leorio's pride clashing with his exhaustion. He heard Kurapika's stern encouragement and Gon's unwavering faith.
Five minutes later, the sound of heavy, desperate footsteps returned.
Leorio was running again, fueled by a raw, irrational burst of adrenaline that defied Gabriel's biological model.
Gabriel's eyes flickered. 'Interesting. Human willpower as a variable that disrupts statistical probability. I will have to account for that in future models.'
As they approached the fifty-kilometer mark, the tunnel began to curve sharply upward.
The stairs appeared—thousands of them, disappearing into a vertical darkness.
This was the "Spirit Breaker."
[Ding! Milestone Sign-In: The Stairway to the Surface.]
[Reward: 'Geppo' (Source: One Piece - Moonwalk) — The ability to kick the air itself to jump or 'walk' through the sky.]
Gabriel felt his calf muscles tighten and reform, the fibers becoming denser, more elastic. He looked at the stairs. While others began the grueling climb, dragging their bodies up each step, Gabriel's movements became even more fluid.
He wasn't even using the stairs for support; he was merely tapping them with his toes, his body propelled by the subtle air-pressure of Geppo.
He was now at the very front of the middle pack, closing the gap with the elites.
He passed a man who was using two daggers as pitons to climb the walls.
He passed a group of three brothers moving in a synchronized formation. They all looked at him with a mixture of confusion and fear. He looked less like a boy and more like a ghost rising toward the surface.
Then, he felt it.
A sharp, needle-like sensation on the back of his neck.
He didn't need Observation Haki to know who was watching. Near the top of the current flight of stairs, leaning casually against a stone pillar, was the man with the pins in his face—Gittarackur.
Gabriel's Six Eyes saw through the pins immediately. He saw the long, dark hair and the dead, vacant eyes of Illumi Zoldyck.
The assassin was observing Gabriel's "Weightless Stride" with professional interest.
Gabriel didn't look up. He didn't acknowledge the threat. He simply passed the assassin, their auras brushing for a fraction of a second.
Illumi's needles twitched. He felt a chill—not the chill of a cold room, but the chill of a vacuum. Gabriel's aura didn't feel "strong" in the traditional sense; it felt infinite. It was like looking into a well that had no bottom.
Gabriel reached the landing. He was now just a few dozen meters behind Satotz.
The air was changing. The damp, recycled scent of the tunnel was being replaced by something more complex—the smell of wet soil, rotting vegetation, and the musk of predators.
"The end of the tunnel is in sight," Satotz announced, his voice steady as if he hadn't just run fifty kilometers.
Gabriel looked ahead. A white dot of natural light appeared in the distance.
He checked his internal clock. They were at the sixty-kilometer mark. According to his map of the island, the tunnel was nearly finished, but the true trial was the environment waiting outside.
He glanced back. Gon, Killua, Kurapika, and a nearly-dead Leorio were emerging from the stairs. They had made it through the first filter.
Gabriel turned his eyes back to the light. He felt the Singularity Engine humming in his chest, sensing the massive narrative weight of the "Swindlers' Swamp" ahead.
'The tunnel was for the weak,' Gabriel thought, his face remaining a mask of cold indifference. 'The swamp is for the hunters.'
He took one final breath of the Sun, his lungs glowing with a faint, internal heat. He was ready to stop running and start dismantling the obstacles in his path.